Name: __________________________________
Date: ___________________________________
Flynt - ____ Period
____th Grade Science
Plate Tectonics causes stress,
stress causes strain,
and strain results in structures!
Many geologists consider it important for introductory students to understand that visible structures are a record of the stress and physical conditions
in the Earth. As a result, the differences between stress, strain, and the structures formed during strain are key concepts you need to understand and
be able to connect!

Stress is a force acting on a rock.
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Stress is a measure of the magnitude and direction of a deforming force.
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Stress occurs whenever any solid (including rock in the Earth’s lithosphere) is subjected to a squeezing, stretching, or twisting force.
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The term “stress” is used rather than “pressure” because stress includes the concept of direction, including maximum and minimum
stress directions.
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Stress has the same units as pressure (force per unit area), and also has a direction (i.e., it is a vector, just like a force).

Stress can be uniform in all directions (hydrostatic) or can take on the forms of compression, tension, or shear.
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The three main types of stress: compression, tension, and shear.
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Stress can cause strain, if it is sufficient to overcome the strength of the object that is under stress.

Illustrate the three main types of stress:
Strain is a change in shape or size resulting from applied forces (deformation).

Strain is a measure of the changes in length, volume, and shape in a stressed material. When a substance is stressed, it responds by
changing size or shape, or both. The term used to describe change in shape or size is strain.

Deformation is synonymous with strain. Deformation occurs as a response to stress, and it is quantified as strain.
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Strain can be elastic, brittle, or ductile. (Ductile deformation is also called plastic deformation.)

Example: Rocks along a fault line can experience elastic strain for thousands of years before they break or fracture
(brittle deformation). The actual fracturing of the rock causes an earthquake. It is the chemical and physical properties of
the rock that determines how much elastic strain the rock can endure before it “snaps.” When crustal rocks deform
elastically for long periods of time rather than immediately break, the result is large, devastating earthquakes. The
composition of some lithospheric rocks allow them undergo limited ductile deformation, which lessens the potential,
frequency, and strength, or an earthquake.

Rocks do not strain unless they are placed under stress. Any rock can be strained.

Elastic strain is temporary. Both ductile and brittle strain/deformation are permanent.

Define and describe each of the three main types of strain:

Structures in geology are deformation features that result from permanent (brittle or ductile) strain.
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Examples of structures that result from permanent (brittle or ductile) strain include folds and faults.
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Landforms—specifically mountains (and sometimes valleys)—originate from faulting and/or folding.
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Geologists use faults and folds to identify the type of stress a rock experienced, as well as the conditions of stress it suffered (or
enjoyed, depending on your point of view).


Illustrate each of the four major types of faults: normal, reverse, thrust, and strike-slip.

Illustrate each the three main types of folds/folded structures: monocline, anticline, and syncline.
Plate Tectonics—the movement of lithospheric plates due to convection in the asthenosphere—is the main cause of stress forces that lead to
strain (deformation), which in turn leads to structures like faulted and folded mountains.

The direction of the applied stress acting on a piece of lithosphere depends on the chemical composition of the lithosphere
and the motion of the lithospheric plates relative to each other.

All motion is relative—the first step in describing motion is to establish a reference point. All plate motions are described relative to
another tectonic/lithospheric plate.
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Illustrate the three types of motion that occurs at plate boundaries: convergent, divergent, and transform.
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Explain which types of stress are associated with each of the three types of plate boundary motion:

Explain which types of structures might be associated with each type of plate boundary motion: